Method and apparatus for ultrasonic cleaning of teeth



April 2, 1968 A. KURIS ETAL 3,375,320

METHOD AND APPARATUS FOR ULTRASONIC CLEANING OF TEETH A 5 Y z m N e a Rm m T m 5V SU 16. "Q vmM r S g mUA .4 t L 9 J a. A e B h H R .W S Us e 2/W m RE AL Y B M Filed Dec.

United States Patent 3,375,820 METHOD AND APPARATUS FOR ULTRASONICCLEANING F TEETH Arthur Kuris and Lewis Balamuth, New York, N.Y., as-

signors to Cavitron Corporation, a corporation of New York Filed Dec.15, 1965, Ser. No. 513,991 23 Claims. (Cl. 128--62) This inventionrelates to methods and apparatus for oral hygienic care, and moreparticularly to methods and apparatus for personal dental care employingultrasonic energy suitable for regular use in the home.

Within the past several decades, the importance of oral health to theindividuals overall physical well being has been recognized and muchprogress in professional and personal dental care has been made. Alongwith periodic examination and treatment by professionally traineddentists, it has been established that significant benefits are derivedfrom regular dental care performed in the home by the individualhimself. It is universally recognized, for example, that regularbrushing of the teeth, particularly after every meal, serves to dislodgefood particles which ordinarily are retained adjacent the teeth andwhich, if allowed to remain, would cause decay and dental caries. Whenproperly administered, regular brushing also serves to maintain goodcirculation in gingival tissue, thereby lessening the likelihood ofgingival disease, one of the prime causes of premature loss of teeth.Perhaps of less, but nevertheless significant, importance are the stainremoval and brightening actions resulting from regular brushing, whichcontribute noticeably to the appearance of the individual.

Until recent years, personal dental care was effected solely throughmanual brushing, generally with some form of dentifrice. Theeffectiveness of this technique depends in large measure upon theassiduousness of the individual in performing the necessary manualmotions for the required period of time. A proper brushing, which shouldbe performed twice a day or more, requires a certain amount of manualdexterity, as well as patience. The effort is particularly unappealingto children and it is only with great perserverance that parents areable to train their offspring in proper dental care. Furthermore, with aconventional toothbrush it is extremely diflicult, if not impossible toreach into the narrow spaces between the teeth and thus maintain theinterproximal areas free of debris, or to remove foreign particlestrapped at the gingival crest, i.e., the gum line.

In recent years, manually actuated brushes have been replaced inincreasing proportion by motor driven toothbrush devices. Theseimplements take many forms, but all consist basically of an electricmotor powered by battery or from a standard 60 cycle source, and a brushelement which is driven by the motor. The motion imparted to the brushelement may be rotary, longitudinal, or oscillatory, either in alongitudinal or transverse mode, or combinations thereof. In all of thedevices of this type known to the present inventors, the movement of thebrush head itself is effected at a rate of speed related to commercialpower frequencies, i.e., 60 c.p.s., and the brush element may move onthe order of from 60 to 120 times a second.

Such motor driven toothbrushes provide advantages over conventionalmanual brushing, Since a great many more brushing strokes per second areprovided by the powered device, substantially more brushing is performedby the user in a given amount of time. This has the effect of condensingthe time necessary for an adequate brushing to a small fraction of thatrequired when done by hand. Also, since the motor provides the powernecessary to move the brush head in the prescribed manner, it

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is only necessary for the user to guide the brush over the toothsurfaces to achieve proper results. These devices then are appealing inthat they are relatively simple to use and also serve to provide whatamounts to an increased amount of brushing per unit time, as compared toconventional manual brushing.

However, the use of these conventional motor driven toothbrushes doesnot overcome many of the disadvantages of manual brushing. Although asomewhat increased scrubbing action relative to manual brushing occursat those tooth surfaces readily contacted by the bristle ends, stainsand foreign deposits in the interproximal and gingival crest, orgumline, areas are reached no better by the motor driven toothbrush thanby the manually actuated brush. Accordingly, the agents responsible formany dental caries and gingival disease are not removed by substitutionof a conventional motor driven toothbrush for the manually actuatedimplement.

Previous work by the present inventors in the application of ultrasonicenergy to dentistry, has established that ultrasonic energy can beuseful in the care and treatment of teeth. In Patent No. 3,076,904,granted Feb. 5, 1963 for Acoustically Vibrated Material Cutting andRemoving Devices, assigned to the present assignee, there is disclosedan ultrasonically actuated device, which, inter alia, has foundimportant applications in the dental office. The apparatus of the patentutilizes a hardened steel tip vibrated at an ultrasonic rate fordrilling teeth in the treatment of dental caries, and also under propercontrol of the dentist, for the removal of deposits of tartar and scalefrom tooth surfaces. In the use of this tool for the removal of depositsof tartar and scale, it is found that in the wet field supplied by awarm water spray impinging on the tool tip, a relatively gentle peckingat the deposits results in their rapid and efficient removal. Thus thetime consuming, imperfect, and sometimes painful manual scraping usuallyperformed by the dentist in the cleaning of teeth can be avoided.

However, while the benefits of ultrasonic energy have been successfullydemonstrated and are now in wide use in dental offices, no techniques orapparatus employing ultrasonic energy for personal home dental care hasheretofore been devised. As will be appreciated, the dental instrumentdescribed in the aforementioned patent must be carefully manipulated bya skilled dentist or dental technician to avoid injury to the teeth orgingival tissue. It will be recognized of course, that professionaldental treatment is not administered except at relatively long intervalsand the cleaning techniques employed by dentists must be considerablymore powerful than those utilized in daily oral hygienic care performedby the individual at home.

It is the primary object of the present invention to pr0- vide methodsand apparatus employing ultrasonic energy for personal oral hygieniccare which enables significantly better cleaning of teeth and which iscompletely safe for use by untrained adults or children in the home on aregular basis.

It is a further object of this invention to provide novel and improvedcleaning techniques and apparatus for regular personal oral hygieniccare giving excellent cleaning results in the hard to reachinterproximal and gum line areas and in general, in areas around theteeth that are normally relatively inacessible.

Still another object of the present invention is to provide a novel formof apparatus employing ultrasonic energy for use in regular personaloral hygienic care in which the cleaning element or brush itself isreadily replaceable, thereby enabling a single power handle to be usedwith a plurality of cleaning elements.

Yet another object of the present invention is to provide an improvedapparatus for regular personal oral hygienic care, employing ultrasonicenergy, in which the cleaning element itself may be used apart from theremainder of the apparatus as a manually actuated toothbrush.

The present inventors have discovered that, when applied under propercontrol to tooth and gingival surfaces in the human mouth, ultrasonicenergy may be successfully employed for regular oral hygienic carewithout any damage to tooth surfaces or gingival tissues. Theseultrasonic cleaning techniques provide a significantly increasedcleaning ability, particularly in the interproximal and gum line areaswhere presently known brushing techniques are inadequate. Briefiy, inaccordance with the invention, a cleaning member, which preferablyincludes a plurality of individual cleaning elements, such as thebristles on a brush, are vibrated at an ultrasonic rate and manuallymoved over tooth and gingival surfaces under relatively light pressure.Although not necessarily limited thereto, the combined ultrasonic andmanual movement of the cleaning member may be performed in the presenceof a fiuid, such as water added specifically for the purpose, or thenatural fluids present in the human mouth and in the presence of theusual dentifrices such as toothpaste and tooth powder. The uniqueproperties displayed at the tips of an ultrasonically vibrating membersuch as a brush, enable greatly improved cleaning results to beachieved, particularly in areas where manual or conventional motordriven toothbrushes cannot reach. The ultrasonic energy is applied tothe tooth and gingival surfaces such that no damage whatsoever to thesurfaces will result. On the other hand, because of the greatly improvedcleaning power, the buildup of tartar and scale deposits in theinterproximal and subgingival areas is significantly lessened, promotinga much higher degree of dental health than is possible with ordinarymethods of dental hygienic care.

The apparatus in accordance with the invention is comparable in size andconfiguration to conventional motor driven toothbrush implements and iseminently suitable for home use by adults and children alike withoutspecial knowledge or training. The unit is constructed basically ofthree elements. The first, the cleaning member or brush head, may takeseveral different forms but in general is similar to conventionaltoothbrush heads, having a base member onto which are afiixed aplurality of bristles or bristle-like elements. The brush head isrigidly afiixed, such as by screw threads, to one end of a narrow,elongated vibrating element, such as of magnetostrictive piezoelectricor ferrite material, which can be oscillated. In the illustratedembodiment, the elongated member is completely enclosed in anonmagnetic, fluid-impervious material, e.g. plastic, aluminum, etc. andforms with the brush head a brush insert which approximate the size andshape of an ordinary manual toothbrush. In fact, the individual brushinsert may be used in that fashion if for some reason the ultrasonicgenerator apparatus is not available at the moment. It will beunderstood however, that this is but an added benefit of the particularstructure shown and may be'dispensed with if deemed unnecessary.

The third element of the apparatus is the driving handle which is of asize and shape to be held conveniently in the hand. The handle memberincludes an axial bore for receiving in close fitting engagement the endof the brush insert opposite the brush head. A catch is provided in the'bore for holding the brush insert with sufficient force to preventremoval during use, but to allow ready removal by hand. Alternatingelectrical signals are supplied to suitable elements within the handlemember to drive the vibrating element. With the brush insert positionedin the handle member and alternating electrical signals at an ultrasonicfrequency supplied thereto from an oscillator of convenient form,longitudinal vibrations are induced in the transducer portion of theinsert, which in turn vibrates the brush head. As a result of the uniquemounting arrangement, none of the vibratory energy or heat from thetransducer element is transmitted to the hand of the user.

In family use for example, a single handle member and oscillationgenerator would be supplied, together with a number of brush inserts,one for each member of the family. Each user simply inserts his ownpersonal brush insert into the handle prior to cleaning his teeth. Inaddition, the brush heads themselves on the brush inserts may bereplaced periodically as they wear, without the necessity of replacingthe entire transducer element.

The foregoing and other objects, features and advantages of theinvention will become more apparent from the following detaileddescription thereof, when read in conjunction with the accompanyingdrawings in which:

FIGS. 1A, 1B, 2 and 3 illustrate the cleaning apparatus of the presentinvention in relation to a set of human teeth, and are helpful inexplaining the operation of the present invention;

FIG. 4 is an assembled view, in partial cross section, of the cleaningimplement according to the present invention;

FIG. 5 is a sectional view of the brush insert alone illustrating thevarious components thereof;

FIG. 6 is a section through the brush insert of FIG. 5 taken along thelines 6--6; and

FIG. 7 is a sectional view through the magnetostrictive portion of thebrush insert of FIG. 5, taken along the lines 7-7.

Turning now to FIG. 1A, there is illustrated a portion of a dentalcleaning implement in accordance with the invention in operativeposition against the teeth. The cleaning implement 10 will'be describedin detail hereinafter and for present purposes it is sufficient toindicate that it includes a cleaning member or brush head 12 in whichare mounted a plurality of cleaning elements or bristles 14. Each of thelatter may be composed of a plurality of individual bristle filaments14a. It will be seen that the bristles 14 are not perpendicular to themember 12 but slope slightly forwardly with respect thereto. This is notnecessary but, as will become apparent hereinafter, is the moredesirable orientation. A housing 16 of plastic, or other water resistantmaterial may surround the brush head as shown, leaving the bristles 14exposed.

The brush construction thus far described resembles closely an ordinarymanually actuated toothbrush. In accordance with the invention, thebrush portion of the implement 10 is positioned against the teeth in theusual manner duiing the brushing operation. That is, the brush member isinserted in the mouth and positioned adjacent the tooth surfaces with arelatively light pressure such that at any given time, several of thebristles 14 are in contact With tooth surfaces, while others aredisplaced therefrom by varying amounts. As the implement 10 is movedmanually to pass the brush portion across all of the tooth surfaces, thebristles 14 randomly assume positions in contact with and displaced fromtooth surfaces. As in the case of manual brushing, the bristle elements14a rarely assume positions such that they extend deeply into theinterproximal areas 100a. However, they are 'moved across the spacesbetween adjacent teeth as the implement is moved by the user across thetooth surfaces.

While the cleaning implement 10 is being manually moved over the toothsurfaces, much in the manner in which conventional brushing isperformed, the brush head 12 is vibrated at an ultrasonic rate in itslongitudinal direction, as indicated by the two headed arrow in thefigure. Since the bristles 14 are carried in the brush member 12, theytoo vibrate at the ultrasonic frequency. Accordingly, as the bristles 14pass over the tooth surfaces and across the interproximal areas, theends thereof are vibrating at an ultrasonic rate to provide improvedcleaning results. It has been found that with the application ofultrasonic vibrations to the cleaning member 14 at a frequency in theorder of from 15,000 to 40,000 c.p.s., there are obtained at the toothand gingival surfaces improved cleaning results not obtainable withmanual or conventional motor driven toothbrushes.

In considering the action of conventional mechanically driventoothbrushes, it was concluded that its improved cleaning ability ascompared to a manual brush was due simply to an increased scrubbingaction. For example, a mechanically driven brush having a bristle strokeof .125 and operating at a frequency of 120 c.p.s. (both typical values)will have a peak velocity of about 4 feet per second at the bristle tipsand a bristle tip will cover a distance of approximately inches in onesecond. Both values are substantially greater than can be achieved byhand blushing.

A typical ultrasonically driven toothbrush in accordance with thepresent invention would have a bristle stroke of about .001" (actuallysomewhat less) and would operate at a frequency of 20,000 c.p.s. Thiscalculates out to a peak velocity at the bristle tips of approximately 5feet per second and distance traveled by a bristle tip of about inchesper second.

The ultrasonically driven brush however, does differ from motor drivenbrushes in that both the repetition rate of the bristle motion and theaccelerations at the bristle tips are many times greater in theultrasonic brush. In the case of the example given above, the ultrasonicbrush has a repetition rate 167 times greater than the motor drivenbrush and provides a peak acceleration at the bristle tips of some 200times that of the motor driven brush. These latter two factors, uniqueto ultrasonic actuation, are believed to be primarily responsible forthe greatly enhanced cleaning effectiveness exhibited by theultrasonically driven brush of the present invention.

The foreign deposits normally found on teeth may be generallycharacterized as stain, plaque, and calculus or tartar. Stain and tartarare both adherent deposits on teeth while plaque is somewhat softer andless adherent, such as soft food deposits found in the crevices on andbe tween teeth. Observation has indicated that hand brushing has onlylimited ability to remove stain and little or no effect on tartardeposits. Conventional low frequency motor driven tooth brushes aresomewhat more effective in removing stain but are similarly ineffectiveagainst calculus. In both cases, the ability to remove plaque fromrelatively inaccessible areas is limited.

Comparative tests have shown that not only does the ultrasonicallydriven brush remove tartar deposits, where others have been almostcompletely ineffective, but it also removes stain and interproximaldeposits in a significantly superior fashion. The improved cleaningresults are believed traceable to the high repetition rate of vibrationand the peak accelerations available at the bristle tips, in accordancewith the following analysis.

It is known, from observation, that the ultrasonically vibrating bristleclusters are accompanied by a vigorous cavitational action when thecleaning area is wet. This is a direct consequence of the high peakaccelerations and thus introduces a factor not present in other knowntooth cleaning aids. Thus, cavitational action in the interproximalareas of the teeth would tend to remove plaque in a manner analogous tothe way in which a cavitating cleaning liquid removes dirt frominaccessible regions of a complex watch mechanism.

A further cleaning action believed to occur at the tooth surfacessubjected to the action of the ultrasonically vibrating bristles is akinto a material removing method well known in industry as ultrasonicimpact grinding. This effect is exhibited in the presence of highfrequency vibration, minute strokes of vibration, a cavitating liquidfield and a low density of material-removing particles in the liquidfield. To obtain material removal under these conditions, it isnecessary simply to press the vibratory element or elements lightlyagainst the work surface, e.g. a tooth. Where ordinary dentifrices areused, they supply the low density of material-removing particles in thecavitating liquid field. In the event the ultrasonic brushing is carriedout in the presence of a simple liquid, the process will take place assoon as appropriate material-removing particles are present. These maybe provided, for example, by particles of already removed tartar orcalculus suspended in the liquid. Tartar or calculus is a conglomerateof gritty particles which would serve admirably as an agent to removefurther deposits. Moreover, these particles not being as hard as thetooth structure would not cause damage to the teeth.

The superiority of the ultrasonic tooth cleaning techniques andapparatus of the invention over other brushing procedures are believedto result from a combination of the above effects which are unique toultrasonic phenomena. As the toothbrush is moved over the toothsurfaces, the several effects will be exhibited in varying degrees.However, when used daily over a period of time, it can be expected thatsubstantially all of the tooth surfaces will experience the overallimproved cleaning action to an extent that previously deposited stains,calculus and plaque will be removed and the users mouth and teeththereafter will be maintained in a uniquely clean state.

FIG. 1B, which is an enlargement of the encircled portion of FIG. 1A, ishelpful in explaining how the foregoing phenomena are believed to beconcomitantly utilized in accordance with the invention to provide theimproved cleaning results obtained. With the brush member 12 vibratinglongitudinally in the direction indicated by the twoheaded arrow, thetips of individual bristle filaments 14a, which may be inclinedforwardly with respect to the brush head 12, vibrate with orthogonallyrelated components of motion, as indicated by the crossed arrows in thefigure.

In utilizing the brushing implement, the brush head is inserted in themouth in the usual manner and moved across tooth and gingival surfaceswith the bristle clusters 14 in relatively light contact with the toothsurfaces. As the brushing implement is manually moved throughout themouth, the bristle clusters 14 will randomly assume different positionswith respect to the tooth and gingival surfaces. For example, at any onetime it is likely that some of the clusters will be in direct contactwith tooth surfaces while others will be spaced therefrom by varyingamounts depending upon the angles of the tooth surfaces and thedirection of orientation of the brush member. Thus as shown in FIG. 1B,one bristle cluster may be in contact with a tooth, the subsequentbristle cluster may be slightly spaced from an adjacent tooth andfinally a further bristle cluster may be somewhat more distantly spacedfrom the next tooth.

As discussed above, it is evident that different bristle clusters,depending upon their relation to any particular tooth and its immediateenvironment, will be able to exert a variety of tooth and gun cleaningand conditioning influences. Cavitational effects will be engendered bythe various clusters, in differing degrees depending on the spatialdistribution of the clusters and cavitating liquid relative to thevarious aspects of the tooth and gum surface concerned, for example,into the regions such as designated a. The effects inherent in thecombined action of ultrasonically vibrating bristle elements andassociated fluid make the present invention unique in the dental field,and result in a greatly improved cleaning action as compared to thesimple scrubbing provided by mechanical or manually moved brushes.

As the brushing implement is manually moved through the mouth, in muchthe same way as in manual brushing, the bristle clusters will assumedifferent positions with respect to different tooth surfaces. During aperiod of several minutes of brushing, on the average all of the toothsurfaces will be exposed to at least one, and probably all, of theabove-described cleaning actions. Projected over a period of regularuse, such as twice or three times daily, it will be realized that eachof the tooth surfaces, including interproximal areas and gum linesurfaces will be subjected to much more intensive cleaning than isavailable with other know cleaning implements.

FIG. 2 illustrates the position of the brush head with respect to theteeth 100 and gingival tissue 162 during the conventional cleaningoperation. As would be expected, at various times several of the bristleclusters 14 will contact the gingival tissue. The ultrasonic energyavailable at the bristle tips provide several beneficial results.Cavitation and/ or high energy atomization is produced at the area ofcontact between the tooth surface and the gingival tissue enabling theremoval of foreign deposits from this otherwise relatively inaccessiblearea. Such deposits, if not removed, are the prime cause of the severaldiseases of the gingival tissue which ultimately result in the prematureloss of teeth. Application of ultrasonic energy in accordance with thepresent invention serves to remove these deposits before they accumulateand thus alleviates the cause of the difficulty.

A further benefit is bestowed on the gingival tissue itself. As is wellknown, stimulation of the gingival tissue by massage has been foundbeneficial to the overall dental health. The small amplitude, highfrequency motion of the present invention is advantageous for thispurpose since the limited motion avoids damage to the delicate tissueand the high friquency of occurrence provides more stimulation to bloodcirculation than is obtained by brushing with conventional implements.

In the foregoing discussion and in FIGS. 1A, 1B and 2, a cleaning membersuitable for the application of ultrasonic energy to tooth and gingivalsurfaces in accordance with the invention has been indicated asconforming to a conventional toothbrush construction. Thus, a brush headmade up of a plurality of bristle clusters 14 is generally satisfactoryfor this purpose. On the other hand, inasmuch as the intensity ofcavitational action depends in part upon the output area of theultrasonically vibrating element, it is preferable in accordance withthe invention to provide cleaning members having relatively extendedoutput areas. As shown in FIG. 1B this may be accomplished by providingbristle clusters composed of a relatively large number of individualbristle filaments 14a closely spaced to each other and having the freeends cut in the same plane, whereby each bristle cluster presents asubstantially solid output surface. This construction enables theimproved cavitational action to be achieved without interfering with theflexibility of the bristle filaments which contribute to the scrubbingaction.

An alternative form of cleaning member construction is shown in FIG. 3wherein the cleaning elements 20 are relatively thick, single membersextending from the brush head support 12, and having somewhat roundedtips. While not as flexible as the individual filaments 14a shown inFIGS. 1A and 1B, the cleaning elements 20 enable somewhat bettertransmission of ultrasonic vibra .tion to the tips thereof, with theresult that the cavitational action thereat is increased. Such elementsthereby provide a greater cavitational cleaning potential and, in

presenting more ultrasonic energy than thinner filaments will generallyenhance the total tooth cleaning effect.

Regardless of the precise nature of the cleaning elements employed, itis desirable in order to provide adequate cavitational action that thebristle members have a significant component of motion perpendicular tothe tooth surfaces over which they pass. For this reason it has beenfound advantageous to mount the bristle element at an angle other than aright angle to the brush head supporting member 12. As will be apparentfrom a vectorial analysis of the components of motion in the bristleclusters, taking into account the flexibility of the bristle filaments,the nearer the orientation of the bristle clusters to the direction ofvibration of the brush head, the bigger the component of bristlevibration that occurs in the direction longitudinally of the bristlemember. Conversely, the closer the bristle cluster is to perpendicularto the brush head, the greater the component of motion perpendicular tothe direction of the bristle. To accommodate a brush head to theconfiguration of the human mouth may require a compromise between thetwo extremes, and various intermediate angles, such as those shown inFIGS. 1A, 1B and 3 are possible which provide proper ratios of the twocomponents of motion at the bristle tips to achieve the beneficialresults of the invention. Alternatively, some or all of the bristlemembers may be normal to the brush head and various angular bristleorientations on the same brush head may be employed. I

In FIGS. 4 through 7 there is shown an ultrasonically driven toothcleaning implement in accordance with the principles of the presentinvention. As seen best in FIG. 4, the implement 10 comprises two basicelements: a brush insert 22, and a handle element 24 for receiving theinsert 22.

The brush insert 22 is shown in cross-section view in FIG. 5. In theillustrated embodiment, the insert 22 comprises an elongatedmagnetostrictive element 26 formed of a plurality of thin sheets of amagnetostrictive material such as permanickel or Permendur, or any othermaterial capable of mechanically elongating when subjected to a magneticfield. As shown in the sectional view in FIG. 7,

the member 26 is fabricated of a plurality of individual plates whichare insulated from each other and held tightly in stacked relation suchas by rivets (not shown) extending therethrough. In view of the relativedimensions of the magnetostrictive portion 26, it will be seen that uponinsertion in a suitably oriented magnetic field, a significantelongation of the stack will occur. Consequently, upon applicationthereto of a magnetic field whose magnitude varies, the length of thestack 26 will similarly vary. In accordance with known principles, themagnetostrictive stack 26 is made to be of a length equal to an integralnumber of half-wavelengths in the material at the driving frequency. Inthis manner, maximum conversion of energy from the magnetic field tomechanical vibration is achieved. As noted hereinabove, other forms ofelectrical to mechanical transducers, e.g. piezoelectric, ferrites, mayalso be employed in accordance with the present invention.

Rigidly afiixed to one end of the magnetostrictive element 26, such asby welding, is a connecting member 28. This member may be formed of anysuitable material capable of supporting vibrations transmitted theretofrom the magnetostrictive stack and many metals and hard plastics aresuitable for this purpose. However, to operate most efliciently, theconnecting member 28 should be made equal in length to an integralnumber of half-wavelengths in the material at the frequency ofvibration. A suitable material enabling the length of the connectingmember 28 to be maintained within reasonable limits is Monel, but itwill be understood that other materials may also be used.

Preferably, the connecting member 28 is formed to produce at its outputend 28c an amplification of the longitudinal vibrations applied to itsinput end by the magnetostrictive member 26-. To effect this function,the member 28 is formed in two sections 28a and 28b of differingdiameter. The transition from the larger to the smaller diameter occursat a nodal point of vibration, that is, a point along a member whereinlongitudinal motion is a minimum. In a uniform diameter element onehalfwavelength long, such a node would occur at the quarter-wave point, halfway between the ends. By locating the transition point at a nodal plane,proper acoustic impedance transformation takes place and an increasedlongitudinal amplitude of vibration is obtained at the output end 28c. Amore complete discussion of such acoustic impedance transformers may befound in US. Patent No. Re. 25,033 granted August 29, 1961 to Balamuthand Kuris for Vibratory Machine Tool and Vibratory Abrasion Method, andassigned to the present assignee.

The brush supporting member 12 is rigidly affixed to the forward end 280of the connecting member such as by a screw threaded fastening. By thismeans, longitudinal vibrations in the connecting body may be transmittedunimpeded to the brush head 12 and consequently to the bristles 14mounted therein.

Surrounding the magnetostrictive stack 26 and the connecting member 28is a generally cylindrical casing 30 formed of a suitable non-magneticand fluid impervious material, such as plastic or aluminum. The casing30' is structurally rigid and spaced from the peripheral surfaces of thestack 26 and connecting member 28 over substantially their entirelengths so as not to be vibrated therewith. It is tightly secured tothese elements, however, at 30a by squeezing or crimping the casing 30'to grip the corners of the stack 26, as best illustrated in FIG. 7. Thecrimped portion 30w is selected to be at a nodal point of longitudinalmotion of the stack 26 so that no longitudinal vibration is imparted tothe casing 30'.

At the connecting member end of the casing 30, the walls thereof aresomewhat thickened to closely engage the peripheral surface of theenlarged portion 28a of the connecting member. At approximately a nodalpoint of longitudinal motion in the connecting member, a plurality ofinserts 3-2 of rubber or similar resilient material are secured in thecasing and extend therethrough to snugly engage mating depressionsprovided in the outer surface of the connecting member 28. This servesto firmly support the connecting member within the casing 30 in such amanner that no longitudinal vibration is transmitted to the casing 30.The inserts 32 and the closeness of fit between the casing 30 and theouter surface of the connecting member 28 also provide a fluid tightseal between the casing 30 and the connecting member 28.

The end of the casing 30 beyond the magnetostrictive portion 26 isthickened and provided with a transverse slot 34 extending all the waythrough. The base of the slot is somewhat enlarged and generallycircular in cross section to engage a suitably provided pin in thehandle member 24, as will be hereinafter described. The narrowed wallsof the slot enable the entire insert 22 to be firmly, but readilyreleasably engaged in the handle member.

At its opposite end, the casing 30 is provided with a smaller diametershoulder adapted to be engaged by the brush housing 16 which, as shownin FIG. 6, is generally cylindrical in cross section and provided withan opening along its length to allow for protrusion of the bristlemembers 14. The enclosure 16 may also be formed of a plastic material ofhigh resilience, sized so as to firmly engage the reduced diametershoulder of the casing 30. The enclosure 16 need be removed only when itis desired to replace the brush member 12, such as when the bristles 14have been worn to the point where they are no longer effective.

It will be seen that the entire brush insert 22 is selfcontained andincludes only one part subject to wear, i.e., the bristles 14 in thebrush head 12. The latter is arranged to be removed without difficultyand replaced with a new unit whenever necessary. It will also beobserved that the insert 22 may be used in the same manner as theconventional manually actuated toothbrush should the need arise. As willbecome apparent hereinafter, in an implement according to the inventionintended for home use by several members of a household, each member ofthe household would be provided with his personal brush insert 22 whichhe would place in the handle 24 prior to use.

The handle member is a generally cylindrical element preferably formedof an electrically insulating and fluid impervious plastic material,which is provided with a central bore 40 extending axially therethrough.The outer dimensions of the handle 24 are made such as to be comfortablyheld in the hand without causing fatigue.

The handle 24 is formed in two sections, a first section 42 whose outersurface forms the peripheral surface of the handle, and a second portion44 including a tubular extension which fits within the member 42,leaving between the members an annular space extending substantiallyover their entire lengths. Within this annular space is wound a coil 46of insulated wire for establishing the magnetic field. At the rearwardend of the bore in the member 42 is formed a reduced diameter portion 43sized to snugly receive the brush insert 22. A similar portion 45 isprovided at the forward end of the member 44 so that the insert 22 isfirmly supported in the handle 24.

A pin 48 is mounted transversely of the bore rearwardly of the segment43. This pin is rigidly mounted in the plastic of the member 42 and isof a diameter greater than the spacing of the walls of the slot 34 inthe casing 30, but somewhat less than the diameter of the enlarged baseof the slot. The resiliency of the plastic used in the housing 30enables the brush insert 22 to manually forced over the pin 48 by aforce which is sufficient to prevent its voluntary release but which achild is capable of applying. Similarly, the insert 22 may be removedfrom the handle 24 with the proper amount of force.

The ends of the coil 46 are brought out through a conductor 50 and intoa plug connector 52. The latter is provided with a pair of prongs 54suitable for insertion in an appropriate source of electrical energy(not shown). An extension 56 may be cast integrally with the member 42or added thereto to provide a strain relief for the connecting lead 50.

A thumb switch 58 may be provided on the exterior of the handle 24 foropening or closing the coil circuit to control the supply of power tothe cleaning implement. Alternatively, switch means (not shown) may beprovided within the bore 40 to be actuated upon insertion of a brushinsert 22 and conversely deactivated upon removal of the insert. By suchmeans, power waste is minimized.

The complete assembly for use in the home would include, in addition tothe apparatus disclosed in FIGS. 4 and 5, a suitable source ofalternating electrical energy and DC. polarizing current. Such a sourcewould include, for example, a transistorized oscillator capable ofproducing electrical oscillation at a frequency in the ultrasonic rangee.g., between 15,000 and 40,000 c.p.s. Various types of such oscillatorsare known and it is not believed necessary to describe the detailsherein.

Electrical oscillations and direct current from the source are coupledvia the connector 52 and the lead 50 to the coil 46 in the handle 24.There is thus established in the bore 40 of the handle a magnetic fieldwhose magnitude changes at an ultrasonic rate. Upon insertion of thebrush insert 22, the magnetostrictive portion thereof 26 is positionedwithin the magnetic field and in well known manner, provides amechanical longitudinal vibration at the frequency of the magneticfield. This vibration is transmitted via the connecting member 28 to thebrush head 12 and the bristles 14. Since the casing 30 is isolated fromthe longitudinal motion of magnetostrictive stack 26 and the connectingmember 28, no vibrations are coupled therethrough and no damping thereofoccurs when the assembly is held in the hand of the user.

Furthermore, inasmuch as relatively low power is required and theaverage brushing procedure takes only a matter of minutes, the heatgenerated in the magnetostrictive stack 26 is insufiicient to cause anydamage to the apparatus itself or to provide any discomfort to the user.The diameter of the conductor used for the coil 46 is made relativelylarge to minimize heat generation resulting from I R losses.

From the foregoing, it will be evident that the application ofultrasonic energy to tooth and gingival surfaces is effective to providesignificantly improved cleaning action, and, if employed for regulardental care in the home, will result in maintenance of greater dentalhealth than is possible utilizing conventional toothbrushing implements.

The ability of the application of ultrasonic energy to remove foreigndeposits on a massive scale has been demonstrated by the professionalacceptance of the cleaning implement described in the above-mentionedPatent No. 3,076,904. That apparatus, intended only for use by skilleddentists or dental technicians in the dental oflice, utilizes a singlehard, edged metal tool driven by high energy ultrasonic vibrations forthe purpose of performing complex periodontal treatment of gums andteeth as well as for professional prophylaxis. Such an implement, in thehands of unskilled persons, could severely damage both the teeth and thetender gingival tissue.

In accordance with the present invention, however, relatively lowfrequency, small amplitude vibrations are employed to drive a brushingimplement which, as in the case of the conventional toothbrush, is madeup of a material soft with respect to the tooth surfaces. The variousplastics such as nylon, or natural bristles, are suitable for thispurpose. While it is evident that a single use of the present inventionwill provide the dramatic cleaning results available from theprofessional equipment described in the aforementioned patent, itscontinual regular use will significantly lessen the necessity for suchprofessional treatment. Moreover, the use of relatively soft bristlematerials in combination with low energy ultrasonic vibrations rendersthe use of the invention perfectly safe, whereby it may be regularlyemployed by average persons without any special training or skill.Extended periods of application of ultrasonic energy to the tooth andgingival surfaces in accordance with the present invention will have nodeleterious effect on these surfaces.

In addition to the superior cleaning action provided by the invention,several auxiliary benefits of the ultrasonic action have been noted. Themicro-massage of the gingival tissue, discussed hereinabove, contributessignificantly to overall dental health. The ultrasonic action alsoresults in partial sterilization of bacterial-laden areas of the mouthand provides more intimate application of chemical or other agents thatmay be contained in a dentifrice, if employed by the user.

Cavitational action requires for its support a substantially solid filmof a liquid capable of supporting cavitation between the tip of thecleaning member and the tooth surface to be cleaned. This fluid film maybe provided by the natural fluids in the mouth, emission of which isstimulated during the brushing procedure, or if desired, additionalfluid, such as plain water, may be taken into the mouth prior to thebeginning of the brushing procedure. The use of a dentifrice is likewiseoptional. The combination of the cleaning phenomena provided inaccordance with the invention renders the addition of an abrasive suchas is found in many commercial dentifrices, unnecessary. However, theuse of the pleasant tasting and scented liquid, paste or powder may bedesirable for aesthetic reasons.

It will be seen therefore, that in accordance with the invention amethod of utilizing ultrasonic energy for improved dental hygienic careis provided, together with a novel form of apparatus by means of whichthe process may be carried out. Although only one form of the latter hasbeen illustrated, it will be recognized that many modifications thereofmay be made without departing from the spirit of the invention. Forexample, the shape and configuration of the handle member 24 may bechanged radically from that shown and a different form of engaging meansmay be provided in lieu of the pin and slot device illustrated.Moreover, the handle member 24 may be enlarged to accommodate atransistorized oscillatory power supply instead of merely including aconnection to an external source. In the same way, the bristle elements14 may take various configurations ranging from cavitational bristles asshown to relatively broad area elements known as stimudents. Although amagnetostrictive embodiment has been shown, the broad principles orelectrostrictive conversion.

Accordingly, the invention is not intended to be limited except as setforth in the appended claims.

We claim:

1. A method of removing surface, interproximal and gum line foreigndeposits from teeth comprising the steps of positioning adjacent theteeth to be cleaned a cleaning member of a material soft relative to thetooth surfaces and capable of supporting vibrations in the ultrasonicrange, inducing vibrations in said member at a frequency in theultrasonic range, and moving said ultrasonically vibrating cleaningmember relative to said teeth such that it assumes positions in which itis randomly divided between actual contact with and displacement fromthe surfaces of said teeth.

2. A method of removing surface, interproximal and gun line foreigndeposits from teeth comprising the steps of establishing a fluid film onthe tooth surfaces, positioning adjacent the teeth to be cleaned amulti-element cleaning member of a material soft relative to the toothsurfaces and capable of supporting vibrations in the ultrasonic range,inducing variations in the elements of said member at a frequency in theultrasonic range, and moving said ultrasonically vibrating cleaningmember relative to said teeth such that the elements thereof assumepositions in which they are randomly divided between actual contact withand displacement from the surfaces of said teeth.

3. A method of removing surface, interproximal and gum line foreigndeposits from teeth comprising the steps of positioning adjacent theteeth to be cleaned a multielement cleaning member of a material softrelative to the tooth surfaces and capable of supporting vibrations inthe ultrasonic range, inducing in said elements ultrasonic vibrationshaving orthogonally related components of motion, and moving saidultrasonically vibrating cleaning member relative to said teeth suchthat the elements thereof assume positions in which they are randomlydivided between actual contact with and displacement from the surfacesof said teeth.

4. A method of cleaning teeth in the human mouth suitable for regularpersonal hygenic care, comprising the steps of positioning a brushmember in the mouth adjacent the teeth to be cleaned in the presence ofa dentifrice, manually moving said brush element across the surfaces ofthe teeth, and inducting vibrations at an ultrasonic rate in thebristles of the brush while so moving.

5. A method of cleaning teeth in the human mouth suitable for regularpersonal hygienic care, comprising the steps of positioning a brushmember in the mouth adjacent the teeth to be cleaned, manually movingsaid brush element across the surfaces of the teeth while in relativelylight contact therewith, and inducing vibrations at an ultrasonic ratein the bristles of the brush while so moving.

6. A method of cleaning teeth in the human mouth suitable for regularpersonal hygienic care, comprising the steps of positioning a brushmember in the mouth adjacent the teeth to be cleaned, manually movingsaid brush element across the surfaces of said teeth and overinterpoximal and gingival areas with said brush element in relativelylight contact with said tooth and gingival surfaces, and inducingvibrations at an ultrasonic rate in the bristles of the brush memberwhile so moving, the amplitude of said vibrations being insufficient tocause injury to gingival tissue.

7. A method of cleaning teeth in the human mouth suitable for regularpersonal hygienic care, comprising the steps of positioning a brushmember in the mouth adjacent the teeth to becleaned, manually movingsaid brush element acros the surfaces of said teeth and overinterproximal and gingival areas with said brushelement in relativelylight contact with said tooth and gingival sur- 13 faces, and inducingvibrations at an ultrasonic rate in the bristles of the brush memberwhile so moving, thereby to effect scrubbing at an ultrasonic rate onsurfaces contacted by said vibrating bristles and to promotecavitational action at surfaces spaced from said bristles.

8. A method of cleaning teeth in the human mouth suitable for regularpersonal hygienic care, comprising the steps of positioning a brushmember in the mouth adjacent the teeth to be cleaned, manually movingsaid brush element across the surfaces of the teeth, and inducingvibrations in said bristles at a frequency between about 15,000 to about40,000 cycles per second and of an amplitude such that the majorcomponent of motion of said bristles is approximately .001 inch.

9. A method of removing surface, interpoximal and gum line foreigndeposits from teeth in the human mouth comprising the steps ofpositioning a brush member adjacent the teeth to be cleaned, manuallymoving said brush element across the surfaces of said teeth to randomlyshift the bristles thereof between positions in contact with and spacedfrom said tooth surfaces, and inducing in the [bristles of said brushmember vibrations at an ultrasonic rate, whereby there may concomitantlyresult a scrubbing action at an ultrasonic rate on the tooth surfaceswhen in contact with said bristles and cavitational action between saidbristles and said tooth surfaces when said bristles are displacedtherefrom.

10. Apparatus for use in personal dental hygienic care comprising, acleaning member of a material soft relative to human tooth surfaces andcapable of supporting vibrations in the ultrasonic range, said memberbeing adapted to be received within the human mouth and moved acrosstooth and gingival surfaces, means adapted to be held in the hand forgenerating mechanical vibrations at an ultrasonic rate, and means insaid vibration generating means for supporting said cleaning member andinducing ultrasonic vibrations therein.

11. Apparatus for use in personal dental hygienic care comprising, acleaning member of a material soft relative to human tooth surfaces andcapable of supporting vibrations in the ultrasonic range, said memberbeing adapted to be received within the human mouth and moved acrosstooth and gingival surfaces, transducer means adapted to be held in thehand for converting electrical energy into mechanical vibrations at anultrasonic rate, and means in said transducer for supporting saidcleaning member and inducing ultrasonic vibrations therein.

12. Apparatus for use in personal dental hygienic care comprising, acleaning member having a plurality of individual cleaning elements of amaterial soft relative to human tooth surfaces and capable of supportingvibrations in the ultrasonic range, said member being adapted to bereceived within the human mouth and the elements thereof moved acrossthe tooth and gingival surfaces, transducer means adapted to be held inthe hand for converting electrical energy into mechanical vibrations atan ultrasonic rate, and means in said transducer for supporting saidcleaning member and inducing ultrasonic vibrations in said cleaningelements.

13. Apparatus for use in personal dental hygienic care comprising, acleaning member of a material soft relative to human tooth surfaces andcapable of supporting vibrations in the ultrasonic range, said memberbeing adapted to be received within the human mouth and moved acrosstooth and gingival surfaces, electroacoustic transducer means includinga first member adapted to be held in the hand and to be supplied withalternating electrical energy at a frequency in the ultrasonic range, asecond member responsive to alternating electrical energy tomechanically vibrate at the frequency of said energy, means on saidsecond member to support said cleaning member and impart vibrationsthereto, and means in said first member for receiving said second memberin readily releasable fashion, said second member converting theelectrical energy supplied to said first member into mechanicalvibrations when received therein, whereby ultrasonic vibrations areinduced in said cleaning member.

14. Apparatus for use in personal dental hygienic care comprising, acleaning member of a material soft relative to human tooth surfaces andcapable of supporting vibrations in the ultrasonic range, said memberbeing adapted to be received within the human mouth and moved acrosstooth and gingival surfaces, an elongated member formed at least in partof a magnetostrictive material, means to couple said cleaning member toone end of said elongated member, an additional member adapted to beheld in the hand and including coil means for creating an alternatingmagnetic field at the frequency of alternating current signals appliedthereto, said additional means further including means to releasablyreceive said elongated member such that said magnetostrictive portionthereof is disposed in said magnetic field, whereby upon application ofalternating current signals to said coil, said elongated membermechanically vibrates in a longitudinal direction and vibrations areinduced in said cleaning member.

15. Apparatus for use in personal dental hygienic care comprising, abrush member adapted to be received within the human mouth and movedacross tooth and gingival surfaces, an elongated member formed at leastin part of a magnetostrictive material, means to rigidly couple saidbrush member to one end of said elongated member, a casing ofnon-magnetic material enclosing at least said magnetostrictive portionof said member in fluid-tight manner, an additional member adapted to beheld in the hand and including coil means for creating an alternatingmagnetic field at the frequency of alternating electrical signalsapplied thereto, said additional means further including means toreleasably receive said elongated member such that said magnetostrictiveportion thereof is disposed in said magnetic field, whereby uponapplication of alternating electrical signals to said coil, saidelongated member mechanically vibrates in a longitudinal direction andvibrations are induced in the bristles of said brush member.

16. Apparatus for use in personal dental hygienic care comprising, abrush member adapted to be received within the human mouth and movedacross tooth and gingival surfaces, an elongated member formed at leastin part of an electroacoustic transducing material, means to rigidlycouple said brush member to one end of said elongated member, anadditional member adapted to be held in the hand and of a length shorterthan said elongated member, an opening in said additional member adaptedto receive at least the electroacoustic transducing portion of saidelongated member, means in said opening to engage said elongated memberin a readily releasable fashion, energy supply means in said additionalmember adjacent said opening, and means to connect alternatingelectrical signals to said energy supply means for coupling to saidelectroacoustic transducing portion, whereby mechanical vibrations atthe frequency of said alternating signals are induced in said elongatedmember and said brush member.

17. Apparatus for use in personal dental hygienic care comprising, abrush member adapted to be received within the human mouth and movedacross tooth and gingival surfaces, an elongated member formed at leastin part of a magnetostrictive material, means to rigidly couple saidbrush member to one end of said elongated member, an additional memberof electrically insulating material adapted to be held in the hand andof a length shorter than said elongated member, an elongated bore insaid additional member adapted to receive at least the magnetostrictiveportion of said elongated member, means in said bore to engage saidelongated member in readily releasable fashion, coil means embedded insaid additional member and surroundingsaid bore, and means to supplyalternating electrical signals to said coil means to establish analternating magnetic field in said bore, whereby 15 mechanicalvibrations at the frequency of said alternating signals are induced insaid elongated member and said brush member.

18. Apparatus for use in personal dental hygiene care comprising, abrush member adapted to be received within the human mouth and movedacross tooth and gingival surfaces, an elongated member formed at leastin part of a magnetostrictive material, means to rigidly couple saidbrush member to one end of said elongated memher, a casing ofnon-magnetic material enclosing at least said magnetostrictive portionof said member in fluidtightmanner, an additional member of electricallyinsulating material adapted to be held in the hand and of a lengthshorter than said elongated member, an elongated bore in said additionalmember adapted to receive at least the magnetostrictive portion of saidelongated member, means in said bore to engage said elongated member inreadily releasable fashion, coil means embedded in said additionalmember and surrounding said bore, and means to supply alternatingelectrical signals to said coil means to establish an alternatingmagneto field in said bore, whereby mechanical vibrations at thefrequency of said alternating signals are induced in said elongatedmember and said brush member.

19. A personal brush insert for use with an ultrasonic dental cleaningimplement having a handle member in cluding coil means adapted to beenergized from a source of alternating electrical signals and means toengage the insert in readily releasable fashion, said brush insertcomprising, a brush member adapted to be received within the human mouthand moved across tooth and gingival surfaces, an elongated member ofmagnetostrictive material having a length equal substantially to anintegral number of quarter wavelengths in the material at the frequencyof said alternating signals, a connecting member of vibrationtransmitting material fixed at one end to one end of saidmagnetostrictive member and having the other end adapted to rigidlysupport said brush mem- 16 ber in vibration transmitting relationship,said connecting member being of a length substantially equal to anintegral number of quarter wavelengths in the material at the frequencyof said alternating frequency, and a fluid impervious casing enclosingat least said magnetostrictive member.

20. A personal brush insert according to claim 19, wherein said casingis spaced from said magnetostrictive member over substantially itsentire surface and is fastened thereto at a point along the length ofsaid magnetostrictive member at which a node of longitudinal vibrationoccurs.

21. A personal brush insert according to claim 20 in which said casingalso encloses said connecting member in spaced relation thereto and afluid-tight seal is provided between said casing and said connectingmember at a point along said connecting member at which a node oflongitudinal motion occurs.

22. A personal brush insert according to claim 21 in which said casingis formed of a non-magnetic material and is provided at its end remotefrom said brush member with a slot adapted to engage a pin in saidhandle member in readily releasable fashion.

23. A personal brush insert according to claim 19 in which saidconnecting member comprises an acoustic impedance transformer foramplifying vibrations provided by said magnetostrictive member.

References Cited UNITED STATES PATENTS 2,187,076 1/1940 Erickson 128-622,874,470 2/1959 Richards l28-24 XR 3,076,904 2/ 1963 Kleesattel et al.3 1026 3,213,471 10/1965 Freeman 12862 XR 3,213,537 10/1965 Balamuth etal. 3l()26 XR L. W. TRAPP, Primary Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,375,820 April 2, 1968 Arthur Kuris et a1.

It is certified that error appears in the above identified patent andthat said Letters Patent are hereby corrected as shown below:

Column 10, line 16, after "to" insert be Column 11, line 20, after"will" insert not Column 12, line 24, "variations" should readvibrations line 44, "hygenic" should read hygienic Column 15, line 4,"hygene" should read hygienic Signed and sealed this 12th day of August1969.

(SEAL) Attest:

Edward M. Fletcher, Jr. E.

Attesting Officer Commissioner of Patents

4. A METHOD OF CLEANING TEETH IN THE HUMAN MOUTH SUITABLE FOR REGULARPERSONAL HYGIENIC CARE, COMPRISING THE STEPS OF POSITIONING A BRUSHMEMBER IN THE MOUTH ADJACENT THE TEETH TO BE CLEANED IN THE PRESENCE OFA DENTIFRICE, MANUALLY MOVING SAID BRUSH ELEMENT ACROSS THE SUR-